5 Replies Latest reply on Jan 23, 2009 6:45 PM by the chuck

    IIR or FIR type filters

    the chuck Level 1
      Is it possible to do IIR type filters via PixelBender? I'm thinking that it is not, because most IIR filters require the previous sample's result:

      Here is the standard Butterworth IIR filter equation for a 2-pole Lowpass Filter:
      y[n] = output
      x[n] = input
      aN = coefficient
      bN = coefficient

      y[n] = a0*x[n] + a1*x[n-1] + a2*x[n-2] - b1*y[n-1] - b2*y[n-2]

      As you can see, the filter requires the calculated output of the previous calculation in order to compute the current output.

      in PixelBender, this would be like saying:
      Output[25] = a0*input[25] + a1*input[24] + a2*input[23] - b1*Output[24] - b2*Output[23].

      I'm hoping this is wrong, but there is no way for pixelBender to see a calculated pixel and use it to calculate a separate pixel, correct?

      I'll have to look for a Finite Impulse Response 2pole lowpass filter if there is no way around this, as they don't require already calculated data as part of the input.